Purpose :
Glaucoma causes a reduction in retinal nerve fiber layer thickness (RNFLt) measured around the optic nerve head (ONH). This study was conducted to evaluate the correlation between RNFLt and posterior pole retinal thickness (PPt) using spectral domain ocular coherence tomography (OCT) in Asian subjects with and without glaucoma, across various refractive error groups.

Methods :
This was an observational case-control study. PPt and RNFLt was measured by OCT in 96 subjects with moderate-severe glaucoma and 189 controls without glaucoma or any macular pathology. Humphrey Visual Field (HVF) 24-2 was performed in all subjects. Correlation was obtained between PP, RNFL and mean deviation (MD) on HVF across various refractive error groups – hyperopia (+0.01 to +10 D), emmetropia/low myopia (0 to -2.99D), moderate myopes (-3.0 to -5.99 D) and high myopes (-6.0 D or more).

Results :
Mean global RNFLt was 62.1 microns in glaucomatous subjects and 98.0 microns in controls (p<0.05). Mean average PPt was 267.1 microns and 287.0 microns in glaucomatous and control subjects respectively (p<0.05). After adjusting for age, global RNFLt and average PPt was significantly lower in subjects with glaucoma against controls across all categories of refractive error. Macular average PPt and global RNFLt had a moderate correlation in both glaucoma (rho=0.488, p<0.001) and control (rho=0.497, p<0.001) groups. HVF MD had a moderate correlation (rho=0.479, p < 0.05) with the global RNFLt in the glaucoma group but weak correlation (rho=0.183, p < 0.05) in the control group. HVF MD also showed poor correlation with average PPt amongst both the glaucoma (rho=0.261,p<0.05) and control (rho=0.186,p<0.05) groups.

Conclusions :
This is the first study to date specifically analyzing OCT PPt values in relation to structural (RNFL) and functional (HVF MD) parameters in glaucoma subjects with various degrees of refractive error. Glaucomatous subjects had significantly lower PPt and RNFLt than controls across various refractive error groups including those with high myopia. PPt and RNFLT had moderate correlation in glaucoma subjects. HVF MD showed moderate correlation with RNFLt but not PPt in glaucoma subjects. HVF 10-2 MD might have revealed a better correlation OCT PPt values. It is possible that HVF 24-2 might not be sensitive enough in detecting early glaucomatous damage that might be revealed by thinner PPt.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.